Long-hypothesized 'next generation wonder material' created for first time

For over a decade, scientists have attempted to synthesize a new form of carbon called graphyne with limited success. However, owing to recent study from the University of Colorado Boulder, that endeavor is now over.

Scientists have long been interested in graphyne because of its similarities to graphene, a "wonder material" that is highly valued by industry and whose study was even given the Nobel Prize in Physics in 2010. Only a few bits have ever been generated until this, despite decades of labor and thinking.

This study, published in Nature Synthesis last week, solves a long-standing vacuum in carbon material science, potentially opening up entirely new avenues for research in electronics, optics, and semiconducting materials.

"The whole audience, the whole field, is really excited that this long-standing problem, or this imaginary material, is finally getting realized," said Yiming Hu, the paper's principal author and a chemistry PhD graduate student in 2022.

Because of carbon's utility in industry and adaptability, scientists have long been interested in creating new or unique carbon allotropes, or forms of carbon.

Carbon allotropes can be built in a variety of ways depending on how sp2, sp3, and sp hybridized carbon (or the various ways carbon atoms can link to other elements) and their accompanying bonds are used. Graphite (used in pencils and batteries) and diamonds, both made of sp2 carbon, are the most well-known carbon allotropes.

Over the years, scientists have successfully synthesized many allotropes using classic chemistry methods, including fullerene (for which the Nobel Prize in Chemistry was awarded in 1996) and graphene.

However, these technologies do not allow for the large-scale production of multiple forms of carbon, which is required for graphyne, leaving the postulated material—which is thought to have unique electron conducting, mechanical, and optical properties—to remain just that: a theory.

But it was this demand for the unconventional that prompted people in the field to contact Wei Zhang's lab group.

Zhang, a chemistry professor at CU Boulder, is interested in reversible chemistry, which allows bonds to self-correct, permitting the production of unique ordered structures, or lattices, such as synthetic DNA-like polymers.

Zhang and his lab group decided to give it a shot after being approached.

Creating graphyne is a "really old, long-standing question, but since the synthetic tools were limited, the interest went down," according to Hu, a Ph.D. student in Zhang's lab group. "We brought out the problem again and used a new tool to solve an old problem that is really important." 

The team used an organic reaction called alkyne metathesis, which involves the redistribution, or cutting and reforming, of alkyne chemical bonds (a type of hydrocarbon with at least one carbon-carbon triple covalent bond), as well as thermodynamics and kinetic control, to create something that had never been done before: a material with conductivity comparable to graphene but with control.

"There's a pretty big difference (between graphene and graphyne) but in a good way," exlained Zhang. "This could be the next generation wonder material. That's why people are very excited."

While the material has been successfully manufactured, the team is still interested in learning more about the specifics, such as how to create it on a big scale and how it may be manipulated.

"We are really trying to explore this novel material from multiple dimensions, both experimentally and theoretically, from atomic-level to real devices," Zhang said of next steps.

These studies could help researchers figure out how to harness the material's electron-conducting and optical features in industrial applications such as lithium-ion batteries.

"We hope in the future we can lower the costs and simplify the reaction procedure, and then, hopefully, people can really benefit from our research," Hu added.

This work, according to Zhang, could not have been completed without the help of an interdisciplinary team, adding, "Without the support from the physics department, without some support from colleagues, this work probably couldn't be done."
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